DE2943835A1 - NON-CHROMATE CONVERSION COATINGS - Google Patents

Description

2 ^ 43835

RC-H57-MO12 -6-

DAIlT INDUSTRIES IHC., Paramus, Hew Jersey / USA

Addendum to the patent (patent application RC-1 433-HO1 2

"Non-Chromate Convolution Coatings" and

Addition r-ura patent (patent application RC-1 4ö5-11012

¹¹ Nonchroroatkonversionr.be stratifications

both of the same day

Ni entehromat conversion coatings

The formation of chromate coatings outside the machine occurs Surfaces made from various metals such as zinc and cadmium currently the most widely used common technique to obtain the Metal increased gloss and corrosion resistance to lend. In a typical process, the I-Jetallwerkstüclce immersed in an acidic solution containing hexavalent chromium compounds contains, aio rait the IJetall react and thereby the Abusive of a complex gel-like coating or one Films of trivalent chromium and trapped soluble compounds of hexavalent chromium on the metal surface. The coated Yterk pieces are then rinsed and dried under controlled conditions.

Numerous serious disadvantages are inherent in all of these chronate conversion coating processes at. One of these is the relatively short life of the process bath in terms of units of specific coated surface per unit volume of the bathroom. The main reason for the short service life is the kmti-

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—Π—

detailed formation of dissolved trivalent chromium in the; Bad, arises from the oxidation-reduction reactions that between dew I-j'etall and the sea-worthy chromium.

Trivalent 3 chromium ict an impurity in the process; - !, the the effectiveness of the coating is impaired. So if a decreased coating effectiveness is observed, or if the impurities expanded to a prepared state are at least partially involved in a process of this type Replaced freshly made solution and finally discarded completely in favor of a fresh bath.

The application of the exhausted solution is to be regarded as a waste, since the solution still contains considerable proportions of hexavalent chromium. It is only the loss of these values that "adds significantly to the total cost of the coating process", but the depletion of the exhausted solution must be added to these costs as the solutions present significant waste treatment problems. Hexavalent chromium is highly tonic and must be reduced to trivalent chromium, Z..B .. by reaction with Ilatriumhydrosulfit or JTatriumOisuifit and thereafter niedergeochlagen from the solution by adding \ ^T on alkalis, such as sodium carbonate oderl'alk. According to the answer ^: To remove the precipitate and to settle or filter, the trivalent chromium hydroxide, which is concentrated in the center, has to be spread in specially designated zones, since trivalent chromium is still too toxic to be used as an embankment. Considerable waste treatment requirements for used rinsing water also result from the introduction of toxic chemicals from the process bath into the subsequent rinsing water. Although there are summarized processes for the reoxidation and regeneration of the exhausted chromate solutions and the rinsing water, this results for the small business

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') U /, O \: ' IC

ν * ν!

—Ο—

that the developed more refined, and complicated technology- ?! neither practicable ¹ JOCh economically justifiable for solving the problems of waste handling.

In the llauptpatont (patent application RC-1 / \ 55-1-101 2

"iiichtchromri."i; ko ' ⁱ Tvernio: ii; bcschichtunr: -' i "from the same day) '.-,' a new non-toxic conversion coating solution is described which summarizes. ', sulfuric acid, V.' aGcerstof fpero.Tid, a laudable silicate, rjo './ ie a prime prot-iotor, ie certain: Solution treated metal surfaces.

Although the acidic silicate "solution" can be a true solution or not, but rather in the form of a hydrosol can, for the purposes of this invention, the term "Solution" used to encompass a hydrosol as well as a true solution

In addition to the formation of layers of excellent properties, there are many other important advantages of the invention which are described below. A ". Dor is the same long life of the pußeroröcntiich üeschichtungslöGiing, v; o they favor eir.er fresh solution VorV / orf r: is Fs has been found that the solutions for the treatment of up to approximately 18 b m '" spezifisoher surface area per 1 are suitable, which is far superior to the typical ^T : .'ert of approx. 20 r /, '/ 1 , which is obtained with the usual chroaat coating baths.

Another and related advantage is that, apart from some build-up of dissolved metal in the solution, no disadvantageous residues are formed here and v; ^v hre: iä of use; will be accumulated:] as it is! "all with the usual clock-month coating solutions in which trivalent chromium is very

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ORIGINAL INSPECTED

- builds up quickly.

-The most essential advantage, however, is the non-to: ische iiaiur the system, which greatly facilitates the waste removal of the exhausted solution ¹ - "!"! From the conversion process. Rinsing water can usually be applied without any necessary treatment. The exhausted coating baths are mv with lime - legal: neutralization and removal of dissolved i-j'o!; all ions and phosphorus treated as a deposition, after settling or other separation, the liquid phase can be safely introduced into the general drainage channels, during the dewatered sludge, which is mainly composed of sludge, can be placed in the municipal debris dump.

One object of the present invention is a new conversion coating to create and a method for their training, with the! coating Ulanz and further improved Corrosion resistance results.

Another object is to provide a non-toxic coating solution to provide superior corrosion resistance for iJetal surfaces.

Another object is to create shiny, decorative workpieces of superior corrosion resistance.

This can be seen in detail from the following description and the examples.

According to the invention, a new conversion coating solution is created which comprises an aqueous solution of about 0.2 g / l to about 45 g / l of free U ₂ SO ^, of about 1.5 g / l to about 53 g / l of H ₂ O ₂ , from about 3 g / l to about 33 g / l SiO ₂ and from about 0.15 g / l to

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ORIGINAL INSPECTED

29435: 5

about 10 g / l minimum :; one dor explained below Organophosphorus compound promoters and about 2 g / L to about 20 g / l of at least one secondary proniotor selected from the C group consisting of ascorbic acid, boric acid, uluconic acid, Glycolic acid, acidic acid and salts of these acids, the organic Phosphorus compound has the following general formula:

wherein X is a group of the formula ZO - P - OZ ₀

¹ Il ² ο

in which Z. and '/, ^ are independently of one another hydrogen, iiatriun or potassium;

ro is 0 or 1;

ρ is 0 or 1;

η -; q is (a) 1 if ρ = 0 or

(b) equal to the number of available bonds resulting from up when ρ = 1;

R ₁ is (aj ^c i ~ ^c a alkyl or C ₁ -C. Hydroxy-substituted alkyl and p = 0; and
(b) C, -C. Allrylene or CiC. hydroxy substituted

Alkylene and ρ = 1;
Rp is selected from (a) α =, in = 1

(b) = ii (CH ₂ ) _r ir =, m = 1 and r is one

ganae number from 2 to 6 i _x c) = ii (CII ₂ ) ₂ . N (CHg) ₂ N =, m = 1

(d) C ₁ -C. Alkylene or C ₁ -C, hydroxy-substituted alkylene, ra = 0 or 1

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The SiOp component usually lies in>'orrnone; soluble silicates VOi ¹ , for example iJatriunsilicate or potassium silicate of predetermined contents a ;. SiO ₂ and iYes ^ O or K _? 0 _o The J-jOlverhältr .: s-BO from SiOp su either Iia _? O or K, O are generally between 1 and 4 and it is preferred to use those silicates in which the iiolverivütnis is at least about 1.8 and preferably at least about 2.2. Ammonium or lithium silicates can also be used to create the SiCU components.

Examples of organophosphorus compounds include C -C alkyl phosphonic acids, C -C. -C. Hydroxyalkylenephosphonic acid, amino-tri-C. -C. -Alkylenphosphonc ^: auras, Cp-C "yQln, ^r len-diarnintctra- (O ₁ -C.-alkylenephosphonic acids ) , diethylenetriaminepenta- (C.-C.-allrylenphosphiionKMuren) v / ie the acidic or neutral! .On sodium or Kaliumnalze any of the above aufgciührten rhcpp'ion acids, ii.ydrojryäthyliden-i, ^{1-diphosphonic:;} ure is the preferred connection.

Pie secondary additives can be either in i'orn or as acidic Salts z.13. provided by sodium, potassium, zinc, etc.

The solution is easy to prepare, ie by first adding sufficient sulfuric acid to at least a larger part of the Au: "filling wax with stirring in order to achieve the desired content of free sulfuric acid and thereby taking into account that a certain i'eil the free acid below, we through the _RIA? 0 or K ^ O units introduced with the silicate :: '. en, is neutralized. the silicate is added with stirring to the cooled sour solution until fully dispersed The remaining components are then added. Preferably the peroxide is added last, but the order of addition can be changed without any detrimental effect, provided that the silicate is acidified with sulfuric acid

030019/0889 ORIGINAL INSPECTED

m * w H \ s ν 'ν. * J

will. before mixing with the hydrogen peroxide, otherwise one Peroxide decomposition takes place.

The "preferred concentrations of these compounds in the aqueous solution are from about 1.8 g / l to about 18 g / l of free H ₂ SO-, from about 7 g / l to about 29 g / l of H ₂ O ₂ , from about 8 g / L to about 18 g / L SiO ₂ , about 0.5 to about 2 g / L of the primary organophosphorus promoter, and about 3 to about 10 g / L of the aforementioned secondary promoter.

In order to give the coated work pieces attractive and permanent colors without damaging the corrosion resistance To influence the coating or the stability of the coating solution, it has been found necessary to cationic triarylmethane dyes that used to be used mainly when coloring IT natural fibers such as paper, Cotton, wool, silk and other metallic dyes were used or conversion coating dyes either impair or impart the stability of the system Coating no color.

The triarylmethane dyes used in accordance with the invention are well known in the art and are referred to as a separate generic group of dyes having a Color Index (CI) in the range of 42.COO to 44.999. They come in a wide variety of colors. Both in solid form and as aqueous solution seeds with solids contents typically in the range from 40 to 50% are commercially available. The WiTkS. *? -! "? ¹ proportion of the dye to be added to the coating solution obviously depends on the desired depth of color. This proportion is typically between about 0.05 and about 2 g / l.

The solution is valuable for training conversational

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on numerous metallic surfaces such as those of Zinc, cadmium, silver, copper, aluminum, magnesium and zinc alloys.

The most common application, however, is in training of coatings on zinc plated articles such as zinc plated Steel articles. The zinc plating provides the steel with cathodic protection against corrosion and the conversion coating further improves the corrosion resistance and capability. reduces the susceptibility to fingerprints and improves the appearance by chemical polishing of the article and by the color imparted to the dye. It is essential that the zinc plating coating prior to coating is relatively smooth and fine-grained and that the thickness of the plating coating is at least 0.005 mn, as a certain; etallemfernuiig takes place when the film is formed. D ^ e preferred Plating thickness is between about 0.003 mm and about 0.02 mm.

Usually, the conversion coating is formed immediately after the last rinse in the plating cycle.For example, the freshly plated articles are immersed in the solution, which is kept at room temperatures, within a period of about 5 seconds to about 300 seconds, in order to obtain the best results, the smoke treatment carried out within a period of about 20 seconds to about 50 seconds in a bath which is kept at temperatures not below about 20 C and not above about 35 ⁰ O. The coated articles are then rinsed, first in cold water and then briefly in warm water to aid in the drying of the films. The hot water rinse has a temperature in the range vcn about 60 ⁰ C to about 70 ⁰ C. The final stage d2s coating process s is a i'rocknungsstufe which may be by any IJittsl that wed? Abrades r dsn soft or rather weak film, yet it exposing to excessive temperatures, that is, temperatures

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Höhcrals etv / a VO ⁰ C. The use of circulating air or a fan are examples of suitable agents in the drying operation; after drying, the layers are completely resistant to damage from abrasion and generally do not require the 12- to 24-hour aging that is necessary with the usual chromate coatings.

The resulting coatings have very good resistance against corrosion, as determined with the recognized accelerated corrosion resistance ASi'iJ 13-117-64.

During the course of the solution Bcschichtungsverfahrcns both ar free sulfuric acid impoverished as well as to Y. ^r asserstoffperoxid and must be supplemented. Monitoring of these values should therefore be carried out on a normal basis to ensure that the concentrations concerned do not fall below their limits and to determine the proportions necessary for supplementation or can be determined by pH-13 determination. To keep the free sulfuric acid within the broad range of about 0.2 to about 45 g / l, the pii - V, ^r ert should be between about 0.5 and about 3.5, and preferably between about 1.0 and about J5.0, which corresponds approximately to a concentration of free sulfuric acid of about 1.8 to about 18 g / l. The hydrogen peroxide concentration is advantageously monitored by means of a common titration of ceramnonium sulfate. The Sil5cat (SiOg) consumption is relatively low compared to the consumption of both free sulfuric acid and hydrogen peroxide and in general neither monitoring (which can be carried out using e.g. colorinetric methods such as the reaction of Silcat with Araraoniun-

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ORlGlNAl. INSPECTEP

roolybdate to form a yellow colored hollybdonil goat. ". r. j

nor the addition during practical life ^ u; r dec ■ Coating bath required. The speeds dec consumption (i.e. the percentage decrease in the consentration per unit of time), the primary and secondary additives is, as has been found, approximately of the same order as the consumption of hydrogen peroxide. Therefore, the supplements of the solutions with these additives are suitably nit at the same time the hydrogen peroxide supplement in to the hydrogen precursor proportional shares carried out. The dye, when present, does not generally require supplementation during the practical life of the coating bath. Monitoring the depth of color quality of the coating becomes easy by visual inspection of the coated article and comparison is carried out against a reference color.

The following examples explain the invention in detail.

The general procedures used in the examples for the preparation of the coating solutions, the test probes, ur.d the formation of the coatings are described below.

The aqueous coating solutions are each prepared in such a way that they contain 2.4 g / l free sulfuric acid, 16.2 g / l SiO ₂ , 11.7 g / l H ₂ O ₂ and 0.35 g / l of a 1-llydroxyethylidene -i, 1-diphosphonic acid contain. The SiOp component was added in the form of sodium silicate (SiO ₂ = 33.2 # w / w; ΐ; _{& 2} 0 = 13.85 jS w / w; and a sufficient excess of sulfuric acid is provided to keep the given contents of free H ₂ SO after neutralization of ITa ₂ O in the uatriurasilicate.

Standard iiull cell steel panels (10 cm 6.8 cm 0.03 cm) were made plated with zinc using a cyanide electrolyte.

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ORIGINAL INSPECTED

After vigorous rinsing and drying, the samples were then washed For 40 seconds iu dipped the coating solution "was exposed to Raurotcr.iporatur. The" treated samples were then rinsed in yiasser and then dried with hot forced air.

The dried coated test samples were then sanded Salr ^ spray corrosion tests in accordance with nit AS'i'iJ i'est B-117-64 subject. The tests have been carried out in a vercchicdenen Time schedule, i.e. 6, 16, 24 and 30 hours. After every tone, the samples were checked for corrosion according to a rating scale from 1 to 10 (1 severe corrosion, 10 no Kor?: Osion; checked.

B p i πυ ie. 1 e 1 b is ^

The beneficial effects of boric acid and zinc gluconate as secondary additives are inclined in these examples. The procedures generally described above were followed with the exception that the solutions of Examples 2 and 3 also contained the additives set out in Table 1, which contains the results of the corrosion tests performed on the glossy coated test samples.

Table 1

example Additive Add.
Cons.
g / l After the corrosion
€ hrs. 24 3t <3, y 7th Control
le 1 No 9 8th Control
le 2 Boric acid VJl 10 8th Control
le 3 Ziinkgluco-
nat VJl 9

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ORIGINAL INSPECTED

Example c 4 bi o .12

In this series of experiments all coating solutions contained triarylmethane dyes in addition to the secondary additives according to Table 2. These dyes used were a mixture of EI DuPont de xienours ¹ liquid dyes Victoria Pure Blue IIOP solution (0.2 ml / 1, Basic Blue 7, CI 42,595) and Paper Blue R Liquid (0.1 ml / 1, Basic "violet" J CI 42,555).

The results of the erosion tests on the shiny, colored, coated test samples are shown in Table 2.

Table 2 Additives Add.
Conc.
g / l extent
16 hours after corrosion
24 hours 30 hours 6th No - 7th 6th 7th Example iir. Boric acid VJl 9 8th 7th Control 4 Boric acid 20th 9 8th 7th VJl Ascorbic acid 5 9 8th 6th Kaliuru-iiatriu'.ij
Tartrate 5 10 8th - 7th Glycolic acid 5 9 9 7th 8th Zn Glucona'ü VJl 9 8th - 9 ITa gluconate VJl 9 7th 10 ITa gluconate +
kai sulfate ( D 3.2 9 8th 11 12th

(1) The proportion of kin in 3.2 g ZnSO ^, in 0.5 1 ° Zn gluconate.

is equivalent

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ORIGINAL INSPECTED

Claims (29)

Dr. F. Zumstein Sr. - Cr. E. Asr, .nann- Cr. R. Koenigsbenjer * ^ O O D Dipl.-Phys. R. Holzbauer - Dipl.-Ing. F. Klitigseiseri - Dr. F. Zumstein jun. PATENTANWÄLTE 8QOO Munich 2 Brauhau ^ ctraße <* Totefon Collective No. 22 5341 "elsgramme Zumpat Telex 529079 RC-H 57-1101? 10 / We patent claims 1. Solution for; .i coating outside the machine, characterized in that it comprises an aqueous solution of about 0.2 g / l to about 45 g / l of free HgSO., About 1.5 g / l to about 58 g / l H ₂ O ₂ , about 3 g / l to about 33 g / l SiO ₂ , about 0.15 g / l to about 10 g / l at least one of the following organophosphorus compounds Pro ") oto: cen and about 2g / 1 to about 20 g / l of at least one secondary provnotor selected from the group consisting of ascorbic acid, boric acid, oluconic acid, glycolic acid, tartaric acid and salts of these acids, the organophosphorus compound having the following general formula wherein X is a group of the formula Z ₁ O - P - OZ ₂ wherein Z ₁ and Z _{2 are} independently hydrogen, sodium or potassium; m is 0 or 1; ρ is 0 or 1; η + q is (a) 1 if ρ = 0 or (b) equal to the number of available bonds originating from R ₂ when ρ = 1; R ₁ is (a) C ₁ -C. Alkyl or C ₁ -C 4 hydroxy-substituted alkyl and p = 0; and (bj C ₁ to C. alkylene or C ₁ -C. hydroxy-substituted alkylene and ρ = 1; 030019/0889 ORIGINAL INSPECTED is selected from (a) U = , m = 1 (b) = 11 (CiI ₂ ; H = , ro = 1 and r is one integer from 2 to 6 (c) = N (CH ₂ J _2. W. (CHg) ₂ N = X ro = 1 and (d) C -C. Alkylene or C ₁ -C. hydroxysubstituted alkylene w = 0 or 1. 2. Solution according to claim 1, characterized in that the concentration to free HpSO. is between about 1.8 g / L and about 18 g / L. 3. Solution according to claim 1, characterized in that the H ₂ O ₂ concentration is between about 7 g / l and about 29 g / l. 4. Solution according to claim 1, characterized in that the SiOp concentration is between about 8 g / l and about 18 g / l. 5. Solution according to claim 1, characterized in that the ? A0 ^ is in the form of liatrium silicate or potassium silicate. 6. Solution according to claim 5, characterized in that the I-j'oIve ratio of SiO ₂ to either L7apO or KpO in the sodium silicate or potassium silicate is kept between about 1 and about 4. 7. Solution according to claim 6, characterized in that the molar ratio is at least about 2., 2. 8. Solution according to claim 1, characterized in that it contains e ^J ; v / a 0.5 to about 2 g / l of organophosphorus compounds. 0300 19/0889 2B43835 9. Solution according to claim 8, characterized in that the organophosphorus compound Is hydroxyalkylenediphosphonic acid. 10. Solution according to claim 9 »characterized in that the organophosphorus compound 1-II-hydroxyethylidene-i, 1-diphosphonic acid isto 11. Löcung according to claim 1, characterized in that the secondary Prouotor added in amounts between about 3 and about 10 g / l will. 12. Solution according to claim 1, characterized in that the secondary Promoter is ascorbic acid. 13. Solution according to claim 1, characterized in that the secondary Promoter. Boric acid is. 14. Solution according to claim 1, characterized in that the secondary Pronjotor is Glj-colic acid. 15. Solution according to claim 1, characterized in that the secondary proiaotor is a salt of gluconic acid. 16. Solution according to claim 1, characterized in that the secondary Promoter is a salt of tartaric acid. 17. Solution according to claim 15, characterized in that the Saliä is zinc gluconate. 18. Solution according to claim 15 »characterized in that the salt is sodium gluconate. 19. Solution according to claim 16, characterized in that the salt is sodium potassium tartrate. 030019/0889 20. Solution according to claim 1, characterized in that it additionally a well:;> one amount of at least one cationic triarylmethane dye contains. 21. Solution according to claim 20, characterized in that the dye concentration is between about 0.05 and about 0.3 g / l Dry base amounts. 22. Solution according to claim 20, characterized in that at least one of the dyes Basic Violet 3 has a Color Index of 42,555. 23. Solution according to claim 20, characterized in that at least one of the! Dyes Basic. Blue 7 with a Color Index of 42,595. 24. Method of forming a corrosion-resistant coating selected outside the machine on metallic surfaces made of zinc, cadmium, silver, copper, aluminum, magnesium and Zinc alloys, the metallic surfaces in a coating solution are immersed and then rinsed and dried, characterized in that the metallic The surface is immersed in the coating solution according to claim 1 25. Process for forming an off-machine corrosion-resistant coating on metal surfaces selected from Zinc, Cadmium, Silver, Copper, Aluminum, Magnesium and Zinl: - alloys, the metallic surfaces in a Besohich processing solution are immersed and then rinsed and dried, characterized in that the metallic surface is immersed in the coating solution according to claim 20. 26, Metallic surface coated by the method of Claim 24. 03 0 019/0889 29Λ3835 27. Metallic surface coated according to the method of To, saying 25. 28. Metallic surface according to claim 26, characterized in that that the metal is zinc plated. 29. Metallic surface according to claim 27, characterized in that that the metal is plated 3ink. 030019/0889